Hands on with the iPhone Micro USB plug and third-party chargers

Last month, an "iPhone Micro USB Adapter" popped up on Apple's British online store. Since then, the little plug has made its way across Europe—but not beyond its borders—and it's not hard to connect the dots between this adapter and the earlier European agreement to make all smartphones use the same Micro USB port for charging. So far, it doesn't look like Apple is going to stop including a power adapter with its iPhones in Europe, but even at Apple's prices (£8 in the UK, €9 elsewhere) the Micro USB plug could be a somewhat cheaper alternative to buying a an additional charger or cable for those who already own one or more third-party chargers.

iPhone Micro USB adapter

The Micro USB plug is very small: just as wide, half as tall, and twice as thick as an SD card. It allows an iPhone be connected to a Micro USB cable instead of the traditional 30-pin connector. The plug supports both syncing and charging, and it's listed as compatible with the iPhone 3G and later.

We took the plug for a spin using an iPhone 4 and and a Blackberry charger, and for good measure, tested a few other chargers and charging methods as well. Charging times varied somewhat, and one charger failed to charge the iPhone at all.

How did things get so complex?

As it turns out, USB power is fraught with hidden complexities. It is generally understood that a garden variety USB port will deliver 500 milliamps at 5 volts, but there are circumstances where a USB port can't deliver 500mA (for instance, when an unpowered USB hub sits between the device and the host). In those cases and before the USB data connection has been configured, a device may only draw 100mA. This is the reason that iPod and iPhone manuals all say to connect the device directly to the computer and not to the USB port on a keyboard, which is only meant to power a mouse. To make matters more complex, Apple computers younger than about four years old make it possible for devices to ask for additional power above the standard 500mA.

Implementing a good deal of USB communication logic just to provide more than 100 milliamps worth of power can add unwanted complexity and cost. As a result, some older and/or cheap devices don't bother with this: the devices simply assume they can draw 500mA, and the chargers are capable of delivering at least that. Ignoring a few corner cases, such as low-powered ports on hubs or keyboards, this works well with devices that need 500mA or less. The trouble is that smartphones have big batteries, and charging those at just 500mA is a lengthy affair—the original iPhone, which has the same charging chip as the fifth-generation iPod, takes 3.5 hours to charge.

To address this issue, the USB Implementers Forum came up with a detailed specification for USB-based battery charging. A charger that follows this specification simply connects the USB data lines together over a resistor. The iPhone (3G or later) or other portable device detects this and knows it's OK to draw as much as 1500mA.

Testing time

That's the theory, and below are some experimental results. In each case, we start with an iPhone 4 with a dead battery. 3G is turned on, Wi-Fi and Bluetooth are turned off and the phone isn't used during charging except to take a screenshot every ten minutes.

I bought my iPhone 4 from the UK; this means I can't plug it in anywhere, so I still use my iPhone 3G charger. This charger will charge the iPhone 4 in approximately 123 minutes. Interestingly, charging the iPhone 4 from a mid-2011 MacBook Air—even with no iTunes syncing—took ten minutes longer at 133 minutes. The System Information/System Report shows the iPhone 4 is granted a total 1000mA power draw. (Surprisingly, this is also true for the 5G iPod.) A mid-2007 MacBook Pro, on the other hand, doesn't show any additional power granted to the iPhone, and charging from that computer takes around 185 minutes.

But enough of that: it's time to move on to the third party chargers. The charger for my Sennheiser Bluetooth headphones is rated for 500mA. When connecting an iPhone with a dead battery, the iPhone will charge for a few minutes showing the "low battery" screen. It then boots up and no longer recognizes the power source. Presumably, this charger leaves the USB data lines disconnected so the iPhone doesn't recognize the charger as a charger and also can't initiate the USB communication protocol. Thus limited to a mere 100mA, the iPhone apparently declines to charge.

I also found a no-name USB charger for some long-forgotten device that is rated for 1000mA, the same as the iPhone 3G and iPhone 4 chargers. Unlike the Sennheiser charger, this one charges the iPhone just fine in about 121 minutes.

Yet another 1000mA USB charger is tiny and white, looking a bit like an Apple knockoff, so presumably made with the iPhone in mind. It charges the iPhone, but it somehow affects the iPhone's touchscreen: gestures are no longer recognized in the correct place on the screen. Fearing that the power was out of spec, I disconnected it to prevent possible damage. However, I saw a forum post from someone reporting the same effect when charging an iPhone from the 2100mA iPad charger, which works fine for others and is officially sanctioned by Apple.

The iPhone 4 charging from a Blackberry charger

But now the real test: charging the iPhone with a 700mA Blackberry charger using Apple's Micro USB adapter. The iPhone went through the usual dead battery routine and after a somewhat slow start and charged at 10 percent per 10 minutes, slightly slower than from the 1000mA chargers and at the same rate as from the MacBook Air. During the last 20 percent of the charging cycle, where charging slows down, the Blackberry charger made up for its slow start and finished after 133 minutes, the same as the MacBook Air.

So, what can we conclude?

First off, all USB chargers are not created equal. This extensive test report from six or so years ago shows this very clearly. While most chargers will charge the iPhone, some simply won't work and a few mess up the touchscreen while charging. In general, try to use a charger rated for (at least) 1000mA, which is more likely to be of a more recent design and therefore to be recognized by the iPhone. A 1000mA charger will also support the fastest charging times, and will reach an 80 percent charge a lot faster.

Most chargers these days have a standard USB type A port that the iPhone's dock connector cable plugs into, so the Micro USB adapter is not exactly an essential accessory. But if you have other devices that have a Micro USB port, then it's a little easier to travel with just a Micro USB cable and this adapter than with separate Micro USB and dock connector cables. Not in the least as unlike the dock connector cable, Micro USB cables are cheap and available in a variety of different lengths. The adapter is also small enough to carry everywhere in case you need to leach some power off of an unsuspecting Blackberry or Android user when your iPhone runs out of juice unexpectedly.

The manufacturers who insist on proprietary ports need to also include a micro-USB port (not a dongle). My Samsung Galaxy Tab has a proprietary port and comes with the world's shortest cable. The cheapest I've found another cable for is $15 which is ridiculous.

My Sandisk Sansa Fuze also has a silly proprietary port, but fortunately the new Fuze+ they came out with went to micro-USB.

I vote with my money these days and do not buy anything that doesn't have micro-USB. I hope everyone else does too.

I don't have an iPad, which is also the reason why I didn't test the iPad charger. But I did try it with 3rd and 5th generation iPods which worked fine so I would assume yes. However, Apple only lists compatibility with the iPhone 3G, 3GS, 4 and 4S. You'll probably be fine using the adapter with an iPad and a 1000 mA or less charger, but the plug and/or cables might overheat at the iPad charger's 2100 mA.

Very interesting. I didn't know that Apple's more recent computers had the ability to provide more power for charging when called upon. (Heck, I didn't know that the USB connection could be so intelligent.)

Very interesting. I didn't know that Apple's more recent computers had the ability to provide more power for charging when called upon. (Heck, I didn't know that the USB connection could be so intelligent.)

It's a shame it has to be so complicated. The EU demanding standardization on the micro-usb is a good start - It will drive the world to a single standard.

But I gotta ask why most devices still use regular USB instead of mini or micro? Why does my mouse need such a big plug?

There's no avoiding the "full size" plug on the computer end. There's a difference between the host connector and the device connector (so you can't ever accidentally connect one hard drive to another and wonder why nothing useful happens). What micro and mini replace is the old (but still common on larger devices like scanners) "B" plug, which is square except for a couple of beveled corners to keep you from plugging it in the wrong way.

Long, questionably acronymed story short: if you don't like the A style plugs that connect to PCs, you need to get your Bluetooth on.

"But if you have other devices that have a Micro USB port, then it's a little easier to travel with just a Micro USB cable and this adapter than with separate Micro USB and dock connector cables."

I don't find this to be true at all. I've noticed that little dongle has a tendency to get lost and buried in my bags, pockets, and/or carrying pouches. It takes me forever to find that little focker every time I want to use it. Any time I'm traveling with a cable because I know I'll need to recharge, I'm going to have a bag with me, I'm better off having the second cable - I'll end up charging both of my phones at the same time anyway.

I got this thing because I thought I'd see a lot more use out of it but it sits there in my accessories pouch, not doing anything.

Actually there are both mini and micro versions of the A port as well, check the wikipedia USB page.

Mini is deprecated, and the micro-A receptacle is used only as a cable extension/plug changer. The Micro-AB receptacle is for mobile devices that support USB On-the-Go, and you'd never see it on a dedicated host.

Older model stuff might still use it, but newer stuff should be coming with micro-USB as standard. I have a pair of WD Elements drives (they're just a good shape, size, host powered etc), one is a fairly old model 320GB one with a mini-USB. My more modern one (actually it's USB3 SS rated) has a micro USB port.

Actually there are both mini and micro versions of the A port as well, check the wikipedia USB page.

Mini is deprecated, and the micro-A receptacle is used only as a cable extension/plug changer. The Micro-AB receptacle is for mobile devices that support USB On-the-Go, and you'd never see it on a dedicated host.

The real question is why is this even necessary? I stopped using my ipod in favor of my android because I didn't want to have two charging cables in my car for the same purpose. As far as I can tell, the proprietary cable and port don't provide any benefit to the user, and only exist to lock the user into the Apple ecosystem.

Same with the ridiculous DisplayPort on my wife's Macbook. The $30 proprietary cable I bought from Apple broke the first time I used it, and the output is exactly the same as both DVI and HDMI; the port is bigger than an HDMI port and doesn't even carry audio! Apple makes nice products, but until they learn to play nice with their competitors, I'll keep far away from their walled garden.

As far as I can tell, the proprietary cable and port don't provide any benefit to the user, and only exist to lock the user into the Apple ecosystem.

The first iPod came with a standard Firewire port... I think the 30-pin connector that Apple introduced in a later iPod model has served the ecosystem well: at least this way you had a fighting chance that you could keep using some of your old peripherals when moving from an iPod to an iPhone and iPad because there was no need to go make incompatible changes to the connector as new functionality such as USB and video out was introduced.

When it turned out that as of the 3G the iPhone was no longer compatible with a number of USB chargers, people cried lock-in, too, but as it turns out Apple just implemented the new USB battery charging spec and the newer iPhones work with chargers that follow that specification.

But yes, the prices for all these adapters and cables are rather high.

I use an Amazon Kindle USB charger (UK type G triangle) to charge just about every USB device, it charges my devices insanely fast, my droid phone (x10) takes a couple of hours on my lappy, with its supplied mains plug it takes roughly the same, with my kindle adaptor it takes just under an hour.Same for every device I've tested on, I dunno what the deal is, or if its particularly healthy, but if I need something charged in a hurry I've not found a better solution.

Family members and friends have caught on and repeatedly attempt to procure it whilst I'm not looking this is the only downside I can think of of the EU standardisation... well that and a drawer full of now useless adaptors to support almost every phone.

Very interesting. I didn't know that Apple's more recent computers had the ability to provide more power for charging when called upon. (Heck, I didn't know that the USB connection could be so intelligent.)

The manufacturers who insist on proprietary ports need to also include a micro-USB port (not a dongle). My Samsung Galaxy Tab has a proprietary port and comes with the world's shortest cable. The cheapest I've found another cable for is $15 which is ridiculous.

You can use a USB extension cord, only a few bucks online. I had a few from my computer desk layout of a few years ago that work like a charm.

The iPad charger works fine with my iPhone 4. I doubt that it charges the phone any faster—that would be limited by the battery and its protective circuitry—but sometimes its convenient to carry one charger that'll handle both the iPhone and iPad.

I've been very happy with the micro USB charging spec. Now I'm able to have one charger for both my work and personal cell phone. I've even built a charger using a dynamo hub and 6 Volt battery on my bicycle. Connecting the data lines together to tell the device to pull as much current as it can was genius, since it makes it very easy to build cheap chargers.

The only complaint is that I think the maximum current permitted is 1A, likely due to resistance in the connector and small gage wire. Another reason why tablet makers are not using it, since the Samsung Galaxy Tab 10.1 has a 2A power supply.

The real question is why is this even necessary? I stopped using my ipod in favor of my android because I didn't want to have two charging cables in my car for the same purpose. As far as I can tell, the proprietary cable and port don't provide any benefit to the user, and only exist to lock the user into the Apple ecosystem.

Completely agree here, I can't stand sony-style proprietary BS. I think micro-usb and usb in general turning into the de facto 3~5V standard for many small electronics (not just phones) is awesome because custom wall warts are a disease that has infected consumers for too long.

Now we just need a 12V standard and not 500 different pins of varying polarity, and everything higher power (50W+) needs to get on the laptop 19V gravy train.

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Same with the ridiculous DisplayPort on my wife's Macbook. The $30 proprietary cable I bought from Apple broke the first time I used it, and the output is exactly the same as both DVI and HDMI; the port is bigger than an HDMI port and doesn't even carry audio! Apple makes nice products, but until they learn to play nice with their competitors, I'll keep far away from their walled garden.

However here you're just wrong.

Displayport is actually an open computer standard (meaning apple has no real control over it) it is royalty free unlike HDMI, it does carry audio and from a technical standpoint it is superior in pretty much every way. Many computers can also output dvi or hdmi through the same port with a 2 dollar dongle. (depends on graphics card, not the port)

The $30 cable is your fault, monoprice and several other places (online of course, nobody buys cables in a store unless they are desperate or unaware) will sell them to you for the same price as all the different dvi and hdmi cables, or typically under ten bucks.

The audio part may be apple's fault (or "design decision") because all the newer dell monitors at work have sound over it. Or you might be doing something wrong, I don't buy their stuff so my experience is limited.

Iljitsch van Beijnum / Iljitsch is a contributing writer at Ars Technica, where he contributes articles about network protocols as well as Apple topics. He is currently finishing his Ph.D work at the telematics department at Universidad Carlos III de Madrid (UC3M) in Spain.